The present invention relates to a refrigerant recovery and recharging system and particularly one for use with vehicle air conditioning systems and which includes automatic purging of air from the supply of refrigerant.
In recent years, the maintenance of vehicle refrigerant systems has been accomplished utilizing closed-circuit recovery devices that prevent the discharge of refrigerant into the atmosphere. Such systems are typically self-contained units with the capability of recovering the refrigerant from the vehicle, filtering contaminants from the refrigerant, and subsequently recharging the system. The equipment used also evacuates the vehicle's refrigerant system prior to recharging. In the past, add-on adapters requiring significant operator interaction and control were required for the filtering of refrigerant during the process. Alternatively, a separate unit was employed for the filtering of refrigerant to remove contaminants, such as water, oil, metal shavings and the like. Such prior methods and equipment were costly and time consuming to use and subject to operator mistake. The flushing and filtering of refrigerants is well known. An improved system, providing an indication when the filtering has been achieved is disclosed in U.S. Pat. No. 5,211,024, the disclosure of which is incorporated herein by reference. A system that accomplishes the flushing process with the remaining recovery evacuation and recharging steps is disclosed in concurrently filed U.S. patent application Ser. No. 09/272,868, filed on Mar. 19, 1999, and entitled REFRIGERANT RECOVERY AND RECHARGING SYSTEM WITH AUTOMATIC FLUSHING, the disclosure of which is incorporated herein by reference.
With refrigerant recovery and recharging systems of all types, the connecting and disconnecting of hoses to and from the refrigerant circuit, such as a vehicle's air conditioning system, allows the entry of a small amount of air into the system which ultimately is collected in the main refrigerant tank during recovering, recycling and flushing cycles of operation. Further, the changing of refrigerant supply tanks may also result in a small amount of contaminant, such as air, being introduced into the system. The air collects in the refrigerant supply tank, typically as a gas, above the liquefied refrigerant in the pressurized tank. In the past, a mechanical air purge valve has been employed to bleed air from the refrigerant tank which process was performed while a vacuum was being pulled on the refrigerator circuit being serviced. The process took nearly 10 minutes during a cycle of operation and proves inadequate when the vacuum time was relatively short or if an extreme amount of air was present. Further, such prior art methods would not provide the user with an indication of the amount of air present in the system.
A portable hand-held system has been employed which overcomes some of the deficiencies of the prior art system and is disclosed in U.S. patent application Ser. No. 08/957,185, filed on Oct. 24, 1997, and entitled REFRIGERANT AIR ANALYZER AND PURGE SYSTEM. With such a system, the amount of air is sensed and can be bleed from the system by connecting to the main refrigerant supply tank. Although such a system is an improvement over the prior mechanical methods employed, there remains a need for an air purging system which is integral with the service unit and which can automatically be employed to purge air from the main refrigerant tank without the need for connecting additional equipment to the service unit and with minimal operator intervention.